1. Field of the Invention
The present invention relates generally to grinder pumps. More particularly, the present invention relates to a novel arrangement of components of grinder pumps including a motor, a grinder mechanism, and a pump assembly.
2. Background Information
Grinder pumps are often used in sewage systems for pumping sewage and include a grinder mechanism for cutting or grinding solids or semisolid matter in the material being pumped. Desirably, grinding solids and/or semisolid matter in the sewage allows the resulting particulate effluent to be transferred through smaller diameter pipes without clogging.
FIG. 1 illustrates a prior art grinder pump 10 which comprises a housing 12 having a motor 20 disposed therein. Motor 20 is connected to a progressing cavity pump 30 which, in turn, is attached to a grinder mechanism 40.
Specifically, motor 20 comprises a shaft 22 which extends from the lower portion of motor 20. Shaft 22 extends through a pump rotor 32 of progressing cavity pump 30 and the lower end of shaft 22 attaches to a grinding head 42 of grinder mechanism 40. Grinding head 42, is essentially supported at position A by being cantilevered from a bearing 24 at position B.
A drawback with the prior art grinder pump illustrated in FIG. 1 is the limited ability to provide and maintain close radial clearance between the cutting portions 44 of grinding head 42 and a stationary grinding ring 46 for efficiently and finely grinding wastes. In particular, the eccentric orbiting of pump rotor 32 within a pump stator 34 of progressing cavity pump 30 induces side loads which limit the ability to safely maintain close cutting tolerances between the cutting portions of the grinding head and grinding ring.
In large progressing cavity pumps, it is often advantageous to allow angular and/or radial compliance or displacement of the rotor shaft to reduce the rate of wear of the pump rotor and/or pump stator. This can be provided through the use of one universal joint for angular displacement of the shaft or two universal joints for angular and radial displacement of the shaft. However, incorporation of a rotor shaft having one or more universal joints in the prior art grinder pump illustrated in FIG. 1 renders properly supporting the grinding head impractical if not impossible.
Examples of prior art grinder pumps having a motor attached to a pump, which, in turn, is attached to a grinder mechanism, are disclosed in U.S. Pat. Nos. 3,667,692 to Grace; 3,938,744 to Allen; 4,000,858 to Rudzinski; 4,014,475 to Grace et al.; 4,378,093 to Keener; 4,911,368 to Nishimori; 5,044,566 to Mitsch; 5,553,794 to Oliver et al.; and 5,562,254 to Sleasman et al.
Therefore, there is a need for novel grinder pumps having a stable, rotating assembly, which enable tighter or smaller radial clearances between the cutting portions of the grinder mechanism to improve cutting efficiency, and/or which enable angular and/or radial displacement of the processing cavity pump without sacrificing cutting efficiency.